The present invention generally relates to oil compositions, primarily to fuel oil and petroleum compositions produced there from susceptible to wax formation at low temperatures, to polymeric imides for use with such fuel oil compositions, and to methods for their manufacture.
Fuel oils and/or petroleum products, whether derived from petroleum or vegetable sources, contain components, e.g., paraffins, alkanes, etc. that at low temperature tend to precipitate as large crystals or spherulites of wax in such a way as to form a gel structure which causes the oil to lose its ability to flow. The lowest temperature at which the fuel will still flow is known as the pour point.
As the temperature of the fuel falls and approaches the pour point, difficulties arise in transporting the fuel through lines and pumps. Further, the wax crystals tend to plug fuel lines, screens, and filters at temperatures above the pour point. These problems are well recognized in the art, and various additives have been proposed, many of which are in commercial use, for depressing the pour point of fuel oils. Similarly, other additives have been proposed and are in commercial use for reducing the size and changing the shape of the wax crystals that do form. Smaller size crystals are desirable since they are less likely to clog a filter. The wax from a diesel fuel, which is primarily an alkane wax, crystallizes as platelets; certain additives inhibit this and cause the wax to adopt an acicular habit, the resulting needles being more likely to pass through a filter than are platelets. The additives may also suspend in the fuel the crystals that have formed, the resulting reduced settling also assisting in prevention of blockages.
Effective wax crystal modification (as measured by cold filter plugging point (CFPP), (ASTM D97-66) and other operability tests, as well as simulated and field performance are known in the art. However, there is a continual need in the art to produce more effective polymers giving improved performance.
Surprisingly, the present inventors have found more effective and economical additives. In particular, applicant has found that certain polymeric imides can effectively and economically be employed as pour point depressants for various grades of crude and fuel oil.